From Blue Bloods to Boston Blue: Andrew Terraciano’s Journey and the New Sean Reagan

Andrew Terraciano grew up before America’s eyes as Sean Reagan on the hit CBS series “Blue Bloods.” For fourteen years, from 2010 to 2024, he portrayed Donnie Wahlberg’s younger son, appearing in nearly 300 episodes and becoming a fixture at the iconic Reagan family dinner table scenes. The role allowed him to share the screen with his real-life brother Tony Terraciano, who played Jack Reagan, Sean’s older sibling. While attending New York University, Andrew expanded his creative repertoire beyond acting, writing and performing in several short films. Now 22, Terraciano seemed poised to continue his role in the Reagan family legacy with the spinoff series “Boston Blue,” but fans were surprised when the new show premiered in October 2024 with actor Mika Amonsen taking over the role of Sean Reagan.

The decision to recast such a familiar character wasn’t made lightly. “Boston Blue” creator Brandon Margolis explained to Variety that while they “love Andrew and the work he did over the years,” the spinoff represents “a new chapter” in the lives of both Sean and his father Danny Reagan. The series explores Sean joining the family profession as a police officer, creating a new dynamic where Danny is now the father of a cop—something he’s never experienced before. Margolis viewed this transition as “an organic opportunity to bring in a new performance with a new energy, to help dramatize that change.” The creative team was excited about the “new storytelling lanes to explore” with fresh casting, despite maintaining the same character and relationship foundation. Margolis praised Amonsen’s portrayal, noting the “vulnerability, yet this desire to prove himself” that the actor brings to Sean.

Following the recasting, Andrew Terraciano has maintained a relatively low profile. He has yet to publicly comment on being replaced in the spinoff, though his Instagram bio still proudly displays “Sean Reagan on CBS’s Blue Bloods.” After taking a break from social media during the transition period, he returned in November with casual photos featuring friends, offering little insight into his professional plans moving forward. The quiet nature of the transition has left many fans wondering about the behind-the-scenes circumstances and what’s next for the actor who literally grew up on their television screens. Despite his silence on the matter, Terraciano’s contribution to the Reagan family legacy remains significant, having portrayed Sean from childhood through young adulthood across more than a decade of storytelling.

While Terraciano has kept his distance from discussing the change, his successor Mika Amonsen has been vocal about the responsibility he feels stepping into such an established role. “I definitely felt a ton of pressure at first,” Amonsen admitted, expressing his desire “to respect Andrew the best I could.” This respect extended to visual choices including hairstyling and certain mannerisms that would maintain continuity with Terraciano’s established portrayal. The casting process moved quickly for Amonsen, who had approximately a week from booking the role before being thrust into production. To prepare, he immersed himself in “Blue Bloods,” particularly focusing on later seasons to understand Sean’s evolution into adulthood and his relationship with his father Danny. This research proved invaluable as Amonsen sought to honor the foundation Terraciano had built while finding room to make the character his own in this new chapter.

What Amonsen discovered during his preparation was surprisingly comforting—he noticed natural similarities between himself and Terraciano, particularly in their “upbeat energy.” This common ground allowed him to feel more authentic in his portrayal rather than forcing a complete transformation. “Watching Andrew’s performance, I actually noticed a lot of similarities just between us as people,” Amonsen shared, which gave him confidence to retain certain aspects of his natural personality in the role. The showrunners Brandon Sonnier and Brandon Margolis have supported this approach, giving Amonsen “a lot of freedom to explore that new dynamic with Donnie” Wahlberg. This balance of respect for the established character while allowing room for fresh interpretation seems to be the guiding philosophy behind the transition, attempting to serve both longtime fans and newcomers to the Reagan family story.

“Boston Blue” represents not just a casting change but an exploration of uncharted territory for the character of Sean Reagan. “We’re really just exploring what would have been,” Amonsen explained, noting that “the exploration of Sean being a cop wasn’t something that was on the table” in the original series. This new professional path creates storytelling possibilities that didn’t previously exist, justifying the fresh approach to the character. While some fans may need time to adjust to seeing a new face in a familiar role, the creative team behind “Boston Blue” hopes the compelling father-son dynamic between Danny and Sean—now both law enforcement officers—will win viewers over as the series continues to air Friday nights at 10 p.m. ET on CBS. Whether Andrew Terraciano will return to acting in new projects remains to be seen, but his fourteen-year contribution to one of television’s most beloved family dramas has secured his place in the hearts of “Blue Bloods” fans everywhere.